The elastic fibers in tissues and organs essential for life become fragmented and frayed in emphysema and arteriosclerosis with loss of elasticity. The causes of decreased elasticity are not yet known, nor are the tissue changes which accompany this loss of elasticity delineated. The aims of this proposed research are to investigate the relationship between loss of elasticity and biochemical changes in the elastic fibers. Elastic fibers from porcine lung will be investigated for a relationship between the components of elastin and elastin-associated-protein (microfibrils), to determine whether a biochemically defined interaction can be discerned. Elastin-rich samples from anatomically defined porcine lung parenchymal tissue will be labelled with tritium using sodium borotritide to also reduce the lysine-derived crosslinks. The outer sheath of the interacting proteins will be obtained by mild, controlled procedures and the peptides purified, using sensitive HPLC techniques. Peptides containing lysine-derived crosslinks which are reduced chemically to both stabilize and radioactively label the crosslink, will be analyzed for the primary amino acid structure. These sequences will be compared with known sequences for connective tissue proteins to identify interactions which may have occurred at these protein interfaces. An interaction between elastin and elastin-associated-proteins could occur during embryogenesis leading to stable lysine-derived crosslinks, which makes impossible the removal of these non-elastin peptides except with hydrolytic procedures. To the extent that lysine-derived crosslink change in quantity or in quality during the disease process or aging, our understanding of initiating factors in these diseases may be increased. In addition, the elastin-associated-protein may be a protective factor for elastin in limiting elastin fiber breakdown in the presence of elastases.